Certain processes for upgrading hydrocarbon feeds using fluorine-containing catalysts generate organic fluorine-containing by-products. These processes may involve reactions such as polymerization and alkylation of relatively low boiling hydrocarbons to produce octane enhancers. The fluorine-containing by-products, which are typically fluoroalkanes, are undesirable because they can decompose at elevated temperatures, for example during fractional distillation or combustion, to form hydrofluoric acid (HF) which is corrosive and toxic. One process of particular interest is the HF alkylation of relatively low-boiling hydrocarbons using hydrofluoric acid to produce higher boiling hydrocarbons used as octane enhancers. Although the precise compositions of the fluoroalkanes are difficult to establish, it is believed they are predominately C4 fluoroalkanes, more particularly 2-fluoro-2-methylpropane (tert-butyl) fluoride. The presence of these light fluoroalkanes in n-butane and other hydrocarbon streams is undesirable and may limit the applicability of liquid petroleum gas (LPG) for some purposes, or result in lower market value.
Various attempts have been made to remove undesirable fluoroalkanes from hydrocarbon streams. For example, U.S. Pat. No. 5,396,022, which is incorporated herein by reference, relates to the defluorination of alkane streams comprising treating an alkane/fluoroalkane stream with an acidic alumina, preferably a sulfur-containing alumina, to reduce the amount of fluoroalkanes in the feed.
Also, U.S. Pat. Nos. 2,347,945 and 2,403,714, both of which are incorporated herein by reference, relate to the removal of organic fluorine compounds from a hydrocarbon stream by contacting the hydrocarbon stream with porous materials, such as alumina gel, activated alumina, dehydrated bauxite, chromium oxide, a mixture of alumina and chromium oxide, metals of the iron group, and the like.
While commercially viable processes exist for removing fluoroalkanes from light hydrocarbon streams, there never-the-less remains a need in the art for ever more efficient and cost effective processes for removing these fluoroalkanes.